The invention relates generally to power-driven conveyors and more particularly to modular plastic conveyor belts.
Modular plastic conveyor belts are widely used in various industries to convey products. Modular plastic conveyor belts are constructed of a series of rows of side-by-side belt modules, or rows of belt modules that span the length of the belt. Hinge openings opposite ends of each row interleave with hinge eyes of consecutive rows. A hinge rod inserted in the interleaved hinge openings connects the rows together at hinge joints into an endless conveyor belt loop.
Certain modular plastic conveyor belts may be designed to follow paths that include straight portions and curved portions. Belts capable of flexing sideways to follow curved paths are referred to as radius belts, or side-flexing belts. As a radius belt negotiates a turn, the belt must fan out because the edge of the belt at the outside of the turn follows a longer path than the edge at the inside of the turn. To enable the belt to fan out, the hinge openings on one end of each row are typically elongated in the direction of belt travel. The elongated openings allow the belt to collapse at the inside of a turn and to spread at the outside.
The requirement of following a curved path causes problems not found in straight-running belts. For example, because the elongated openings of conventional radius belts are identical in length across the width of the belt, few of the hinge element ends at the outside of a turn bear the entire belt pull. On a straight run, the belt pull is distributed across the entire width of the belt. Unless the outer hinge elements are specially bolstered, the belt pull strength rating is limited by the pull strength in a turn, which is often up to ten times less than on a straight. Thus, radius belts must be heavier and stronger than straight-running belts conveying the same load. Because the overall scale of structures and discontinuities on heavier belts is greater than on lighter belts, heavier belts are more likely to trip products such as beverage containers with small feet.